Objective of the study is completion of clinical trials necessary to support FDA approval of the use of 191 Iridium for first-pass radionuclide angiographic measurement of ventricular ejection fraction. Iridium 191m is an ultrashort-lived radionuclide useful in adult radionuclide angiography where repeated measurements with high statistical accuracy are needed. The very short half-life of 191m Ir means that the radiation dose to the patient on a per mCi basis is more than 1,000 times less than that incurred with 99mTc. A larger dose can therefore be administered to improve image resolution and precision. The short half-life also facilitates repeated studies to assess the effects of interventions such as exercise on coronary performance because there is no interference from the previous injection. This study is being conducted in adults to 1) determine the relationship between cardiac function measured at rest and exercise with 191mIr and other measures of cardiac health in longterm survivors of Hodgkin's disease who are at risk for progressive ventricular dysfunction, 2) identify a clinical profile of those patients most likely to have accurate determination of ventricular function and cardiac health with 191mIr and 3) identify and characterize any adverse effects associated with the use of 191mIr for the measurement of ventricular function. Survivors of Hodgkin's disease are at particular risk of cardiac dysfunction because of the cardiotoxic effects of radiation therapy and chemotherapy with anthracyclines. These patients have a high 10 year survival but are now beginning to experience late effects of these therapies which include congestive heart failure, high-grade arrhythmias, and sudden death. The total population at risk from these complications is estimated at more than 75,500 in the U.S. If a relatively non-invasive method can be established to screen these patients before the onset of symptoms, this will have a major impact on the long-term survival of Hodgkin's disease patients.